bug#46397: [PATCH] Re: bug#46397: 27.1; Cannot delete buffer pointing to a file in a path that includes a file

[Matt Armstrong]

Tags: patch

Attached is a rev of my prior patch to add some test coverage for
src/filelock.c.

P.S. my FSF copyright papers are done.

>From 18529d097624e0d4647cf04118d4ce98adc474ba Mon Sep 17 00:00:00 2001
From: Matt Armstrong <matt@rfc20.org>
Date: Mon, 15 Feb 2021 12:59:08 -0800
Subject: [PATCH] Add some test coverage for src/filelock.c (Bug#46397).

* test/src/filelock-tests.el: New file.
---
 test/src/filelock-tests.el | 148 +++++++++++++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 test/src/filelock-tests.el

diff --git a/test/src/filelock-tests.el b/test/src/filelock-tests.el
new file mode 100644
index 0000000000..d9534e2d16
--- /dev/null
+++ b/test/src/filelock-tests.el
@@ -0,0 +1,148 @@
+;;; filelock-tests.el --- test file locking -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2021  Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This file tests code in src/filelock.c and related buffer and file
+;; I/O code.
+
+;;; Code:
+
+(require 'ert)
+
+(defun filelock-tests--supported-p ()
+  "Return t if the current system implements file locking."
+  (not (memq system-type '(ms-dos))))
+
+(defun filelock-tests--call-with-fixture (body)
+  "Call BODY under a standard test fixture.
+See `filelock-tests--with-fixture'."
+  (let* ((test-dir (make-temp-file "filelock-tests-" t))
+         (test-dir-modes (file-modes test-dir)))
+    (unwind-protect
+        (let ((file-name (file-truename
+                          (concat (file-name-as-directory test-dir)
+                                  "file"))))
+          (with-temp-buffer
+            (let ((temp-buffer (current-buffer)))
+              ;; Setting both file names is sufficient to enable file
+              ;; locks.
+              (setq buffer-file-name file-name
+                    buffer-file-truename file-name)
+              (unwind-protect
+                  (let ((create-lockfiles t))
+                    (funcall body))
+                (set-file-modes test-dir test-dir-modes)
+                (when (buffer-live-p temp-buffer)
+                  (with-current-buffer temp-buffer
+                    (set-buffer-modified-p nil)))))))
+      (delete-directory test-dir t nil))))
+
+(defmacro filelock-tests--with-fixture (&rest body)
+  "Create a test fixture evaluate BODY there like `progn'.
+Create a temporary directory, then create a temporary buffer and
+set it the variable `buffer-file-name' and `buffer-file-truename'
+to it, let bind `create-lockfiles' to 't' and evaluate BODY.
+Finally, delete the temporary directory."
+  (declare (indent 0))
+  `(filelock-tests--call-with-fixture
+    (lambda () ,@body)))
+
+(ert-deftest filelock-tests-when-create-lockfiles-nil ()
+  (filelock-tests--with-fixture
+   (let ((create-lockfiles nil))
+     (should (not (file-locked-p buffer-file-truename)))
+     (insert "some text")
+     (lock-buffer)
+     (should (not (file-locked-p buffer-file-truename))))))
+
+(ert-deftest filelock-tests-when-create-lockfiles-t ()
+  (filelock-tests--with-fixture
+    (should (equal t create-lockfiles))
+    (insert "some text")
+    (lock-buffer)
+    ;; Verify 't' explicitly and not any true value; 't' alone means
+    ;; the current process owns the lock.
+    (let ((expected (if (filelock-tests--supported-p)
+                        t
+                      nil)))
+      (should (equal expected (file-locked-p buffer-file-truename)))
+      (unlock-buffer)
+      (should (equal nil (file-locked-p buffer-file-truename))))))
+
+(ert-deftest filelock-tests-file-locked-p-inaccessible-dir ()
+  (skip-unless (filelock-tests--supported-p))
+  (filelock-tests--with-fixture
+    (set-file-modes (file-name-directory (buffer-file-name))
+                    (file-modes-symbolic-to-number "ugo="))
+    (set-buffer-modified-p t)
+    (let ((full-error (should-error (file-locked-p (buffer-file-name))
+                                    :type 'file-error)))
+      (should (equal "Testing file lock" (nth 1 full-error))))))
+
+(ert-deftest filelock-tests-lock-buffer-inaccessible-dir ()
+  (skip-unless (filelock-tests--supported-p))
+  (filelock-tests--with-fixture
+    (let* ((test-dir (file-name-directory (buffer-file-name)))
+           (original-modes (file-modes test-dir)))
+      (set-file-modes test-dir (file-modes-symbolic-to-number "ugo="))
+      (insert "some text")
+      ;; FIXME: (lock-buffer) should signal an error here.
+      (lock-buffer)
+      (set-file-modes test-dir original-modes)
+      (should (equal nil (file-locked-p (buffer-file-name)))))))
+
+(ert-deftest filelock-tests-lock-buffer-dir-not-writeable ()
+  (skip-unless (filelock-tests--supported-p))
+  (filelock-tests--with-fixture
+    (set-file-modes (file-name-directory (buffer-file-name))
+                    (file-modes-symbolic-to-number "u=rx"))
+    (insert "some text")
+    ;; FIXME: (lock-buffer) should signal here, but lock_file() in
+    ;; filelock.c ignores some file system errors; see the related
+    ;; FIXME there.
+    (lock-buffer)
+    (should (equal nil (file-locked-p (buffer-file-name))))))
+
+(ert-deftest filelock-tests-unlock-buffer-inaccessible-dir ()
+  (skip-unless (filelock-tests--supported-p))
+  (filelock-tests--with-fixture
+    (insert "some text")
+    (lock-buffer)
+    (should (file-locked-p (buffer-file-name)))
+    (set-file-modes (file-name-directory (buffer-file-name))
+                    (file-modes-symbolic-to-number "ugo="))
+    (let ((full-error (should-error (unlock-buffer)
+                                    :type 'file-error)))
+      (should (equal "Unlocking file" (nth 1 full-error))))))
+
+(ert-deftest filelock-tests-unlock-buffer-dir-not-writeable ()
+  (skip-unless (filelock-tests--supported-p))
+  (filelock-tests--with-fixture
+    (insert "some text")
+    (should (file-locked-p (buffer-file-name)))
+    (set-file-modes (file-name-directory (buffer-file-name))
+                    (file-modes-symbolic-to-number "u=rx"))
+    (let ((full-error (should-error (unlock-buffer)
+                                    :type 'file-error)))
+      (should (equal "Unlocking file" (nth 1 full-error))))))
+
+(provide 'filelock-tests)
+
+;;; filelock-tests.el ends here
-- 
2.30.0